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Abstract

A circular dichromatic transient absorption difference spectroscopy of transmission-grating-photomasked transient spin grating is developed and formularized. It is very simple in experimental setup and operation, and has high detection sensitivity. It is applied to measure spin diffusion dynamics and excited electron density dependence of spin ambipolar diffusion coefficient in (110) GaAs quantum wells. It is found that the spin ambipolar diffusion coefficient of (110) and (001) GaAs quantum wells is close to each other, but has an opposite dependence tendency on excited electron density. This spectroscopy is expected to have extensive applicability in the measurement of spin transport.

Figures (3)

A profile at y=0 of transient spin-polarized electron distribution excited by a circularly polarized pump pulse through a binary transmission grating. N+, N− and N−-N+ denote spin-up, spin-down and spin-polarized electron distribution. The inset shows experimental geometry with the grating in front of the sample. a and d are the transparent slit width and period of the grating, respectively.

Circular dichromatic transient differential transmission traces taken under a transmision grating added except the transient trace A. (σ+,σ–) and (σ+,σ+) denote the cross- and co-helicity circularly polarized pump and probe, respectively. The solid line in the transient trace E denotes the best fitting to open circles data with Eq. (4).

Spin ambipolar diffusion coefficient, spin and recombination relaxation times as a function of excited electron density per quantum well. The scattered points are experimental data. The lines are guide for eyes.